‰  NOW 20 WPM  ‰   TEXT IS FROM JANUARY 2014 QST  PAGE 65‰

A TRADITIONAL ANALOG FILTER IS MADE NARROWER THAN A FEW HUNDRED HERTZ, IT
SUFFERS FROM RINGING, WHICH MAKES NOISE AND SIGNALS SOUND VERY SIMILAR.
HOWEVER, DR ALLEN KATZ, K2UYH, PROFESSOR OF ELECTRICAL AND COMPUTER
ENGINEERING, IEEE FELLOW, AND A LONGTIME EME OPERATOR SAYS THAT A TRAINED
EAR CAN HAVE EFFECTIVE BANDWIDTH OF PERHAPS 50 HZ SOME EME OPERATORS CAN
HEAR AMAZINGLY WEAK SIGNALS.  A DIGITAL FILTER CAN BE MUCH NARROWER THAN AN
ANALOG ONE WITHOUT ANY RINGING.  THE WATERFALL DISPLAY BREAKS THE BAND UP
INTO MANY NARROW FILTERS AND DISPLAYS THE SIGNAL LEVEL IN EACH ONE.  AFTER
SOME EXPERIMENTING WITH THE HDSDR PROGRAM, I FOUND A FILTER BANDWIDTH OF 3
TO 6 HZ FOR THE WATERFALL DISPLAY BEST FOR FINDING WEAK SIGNALS.  OTHER
PROGRAMS MIGHT HAVE OTHER OPTIMUM VALUES.  SIMPLE SDR MY FIRST SDR
‰  END OF 20 WPM TEXT  ‰  QST DE W1AW  ƒ